Marine tanker



June 26, 1962 R. H. BROWN MARINE TANKER 3 Sheets-Sheet 1 Filed April l, 1958 ntor QON

MARINE TANKER 3 Sheets-Sheet 2 Filed April 1, 195s ln entor @mw 01u-M DMW A ttorneyg R. H. BROWN MAkI NE TANKER June 26, 1962 5 Sheets-Sheet 3 Filed April l, 1958 mw WQ@ miw@ 3Q nl SQ A United States Patent O This invention relates to water-borne tankers, particularly ocean-going tankers, for the transport in liquid form, at low temperature and approximately atmospheric pressure, of substances which are normally in a gaseous state. The gas which comes mainly into question is methane, but the references herein to methane are, lwherever the context allows, to be read as references also to like gases which it may be desirable to transport in the liquid state. Liquid methane can be carried in heavily-insulated tanks made of aluminum magnesium alloy, this material being chosen for its good welding properties and be-YY cause its mechanical properties are not adversely affected by -subjection to the temperature of liquid methane, i.e. approximately minus 260 Fahrenheit (minus 162 centigrade). Should a leak develop in a tank, the liquid methane will rapidly nd its way through the insulation unless very special precautions are taken to prevent it. It is of the utmost importance that a leak should be stopped at the earliest possible moment because at the temperature of liquid methane the mechanical prop- 'erties of steel deteriorate alarmingly. Were the liquid methane to come into contact with'the ships plates, the Vship would no longer be structurally safe. Furthermore, the escaping liquid would rapidly evaporate and give rise to a dangerous concentration -in the hold space of methane gas which, in the presence of air, might easily explode.

It is an object of the invention `to provide rapidly effective emergency means for stopping leaks 'from the methane tanks.

According to the present invention, there is provided a 'marine tanker for the bulk transport in the liquid state at low temperature of methane (or like ordinarily- Agaseous substance), wherein each cargo tank is disposed within a watertight hold compartment, and means are provided for rapidly ooding the space the hold compartment around the tank with water, or other liquid such as oil, which will freeze at a temperature much above the liquifaction temperature of methane.

, When on the occurrence of a leak, the space around the tank in its hold compartment is ooded, the liquid in that space is rapidly frozen by the escaping methane and effectively plugs the leak, and keeps the tank in a safe condition until a permanent repair can be effected.

The above and other features of the invention will be apparent -in the following description, given by way of example, of one embodiment in accordance with the invention, reference being had to the accompanying drawings in which:

FIGURE 1 shows in elevation a marine tanker for the transport of methane, n

FIGURE 2 is a plan showing the arrangement ofthe methane tanks in the holds,

FIGURE 3 is a further plan showing the arrangement of tanks at main deck level, and

FIGURE 4 is a diagram of the layout of the holdflooding piping connections, and

FIGURES 5 and 6 are transverse sections taken on the lines 5-5 and 6-6 of FIGURE 2 respectively.

Referring lirstly to FIGURES 1 and 2, the cargo-carry- 3,040,689 Patented June 26, 1962 ice transverse bulkheads 17. Disposed individually in the hold compartments A11 to 16, in a closely-spacedl row 'rate main hold compartments A11 to 16 by a series of along the fore-and-aft centre line' of the vessel are six main cargo tanks 18 to 23 bearing heavy insulation 180 (FIGURE 5). These main tanks are, for the most part, substantially cylindrical in form with their rprincipal axes vertical, and in general they extend at their widest parts for substantially the whole width of the vessel although tanks 19 and 23 are somewhat less in diameter than tanks 20, 21 and Z2, and the most forward tank 18 is a good deal less still in diameter.

The vessel isY of turret construction, that is to say it has a main deck at the level 24 and a narrower turret deck above at the level 25. Each of the main tanks 18 to 23 extends up through the main deck at level 24, and, with the exception of the tank 20, the portions of the tanks that protrude abovethe main deck are as large in diameter as can be conveniently accommodated within the turret structure 26. To this end, tanks 19, 21, 22 and 23 have stepped-in upper portions 28, 29 30 and 31, but the forward tank 18, being already relatively narrow, does not need to be stepped-in. Each of the six tanks terminates at its upper end in a narrow neck 27 surmonnted by a pump motor housing 32. In the case of the five tanksf18, 19, 21, 22 and 23 the narrow tank neck 27 reaches up through the turret deck at level 25 and the housing 32 is situated on said deck, but the tank 20, for reasons which need not be discussed here, is not as high as the other ive,'having itsrneck 27 terminating only just above/the main deck `level 24 and its pump motor housing 32 disposed on the main deck within the turret structure. s

Owing to the circular plan form of the main tanks 18 to 23, there is an appreciable space below decks between one tank andthe next at opposite sides of the vessel, and in the case of tanks v19 Vto 23 these spaces between are utilised by disposing in them eight additional wing tanks 33 of much smaller capacity and bearing insulation 181 (FIGURE 6). The wing tanks 33 are all cylindrical `with their principal axesvupright, and are located wholly below the main deck level 24. As will be seen in FIGURE 2, the arrangement of bulkheads between the main tanks 19 to 23 is such that'each wing tank 33 has its own individual water-tight hold compartment 34, each of the bulkheads 17 branching, as it were, into two diverging bulkheads 35 to embrace a wing tank as it approaches each side of the hull.

It will be observed that each of the small wing tanks 33 has a diameter only about one-fifth the beam of the ship, and, as can be seen in FIGURE 3, the turret structure 26 and turret deck 25 have a width which is about 60% of the ships beam. In a typical example of a 16,600 ton dead-weight methane tanker, the largest main cargo tanks might have a capacity of the order of 280,- 000 cubic feet, and the wing tanks a capacity of 9,000 cubic feet each. In ya vessel of this order of size the turret width of approximately 60% of the beam affords a working deck on either side that is wide enough for easy working. l f Y As can best .be seen in FIGURE 3, the spaces within the turret structure 26 and between the portions of the main cargo tanks lying therein, are occupied by a cargo liquefaction plant shown in block form at 182 and by tanks on the main deck. Thus there are tanks 80 between the pairs of main tanks 18 and 19, 21 and 22, and 22 and 23, with an additional smaller tank beyond the aft methane cargo tank 23, while between the methane cargo tanks 19 and 21 and over the methane cargo tank 20 there is a further large tank 80 and a compartment' 81 occupied by cargo liquefaction plant shown in block -form at 183. Despite the heavy insulation of the methane cargo tanks, there will be a certain amount of methane .boiling in themduring a voyage, and the i it canbereturned'rto the tanks and the liquid level'kept up. Each main tank 18 to 231is normally kept topped 'v up so that the liquid level is in the comparatively narrow neck 27, whereby both the free liquid surface area for evaporation, and the liquid-tree volume, in each tank are kept as low as possible. Y Y l The'deck tanks 80 will contain oil cargo or water ballast, and their position high up in the ship enables these tanks to be used to control stability so that the ship Will have an easy motion in rough seas. The deck tanks 80 can also be employedea's described hereinafter, for flooding the hold space around a methane cargo tank in the event of the tank springing a leak, whereupon the oil or Water ballast ooding the hold will freeze around the 'leak and stop it. The deck tanks 80 are simply constructed of WeldedV plate, and are rectilinearly-shaped as shown in FIGURE 3, being multi-sided so as to best till the'available spaces, and eachV with a centreline division.

In addition to the methane cargo tanks, and the deck tanks 80, the vessel has, besides further conventional ballast'which will not be described in-det'airl, a number of deep tanks 82, 83. The deep tanks'SZ are in the fore partof the ship, grouped around the fore-most methane tank 1=8, while the tanks 83 are grouped around the aft methane tank 23. The deep tanks 82, 83 may be iilled with 'water ballast, but preferably they'are used for the transport of an oil cargo, in addition tothe liquid methane cargo. In a ship of `about 16,600 tons dead- Weight lthese tanks together with the deck tanks, can carry about 9,300 tons of oil cargo, which is a valuable supplement tothe liquid methane cargo.

The individual'hold compartments 11 to 16 and 34 are all liquid-tight, and all the deck tanks S can be connected to flood the space around any one ot the cargo tanks. Owing to the location of the deck tanks the ooding can be carried out rapidly under gravity, so that this 'emergencyV provision is not dependent on the functioning of-pumpin'gmachinery. The largest of the individual `coterdam compartments, in a tanker of about 16,600 tons methane dead-weight, is of the order of 120,000 cubic feet, and the total capacity of all the deck tanks approximately 130,000 cubic feet, so that there is enough liquid in the deck tanks to ll individual cotter- Y ldam spaces. The deck tanks 80 are Yconnected for illing to the ballastY and oil cargo lines and pump installations of the vessel.

As shown in FIGURE 4, each of the deck tanks 80 is connected by branch pipes 15,0, which include handoperated valves 151, to a Water ballast ring main 152 running along the turret, and'also byfbranch pipes 160, including hand-operated valves 161, to an oil cargo line V1762. The deck tanks are also linked to one another by communicating trunks 170. Further branch pipes A153, also provided with hand-operated valves 154, lead Yfrom the deckvtanks 80 to each of the coierdam spaces 1'1 to 16 and 34 surounding the methane tanks'rlS to 23 and 33.` By this means Iall the water or Yoil'tanks 80 can =be connected to any givenrhold compartment inthe event of a leak of methane, and the tanks 80 ycan jbe recharged through either the ballast main '152er theoil cargo line 162. 'Ilhe oil line `162 has provision for shore connections via cargo oil pumps 171, while the ballast main is vconnected to sea lines via ballast pumps 172. During dooding, air escapes from the holds through gas-freeing lines 173, kwhich lead to mast vents (not shown).

l. In a marine tanker for the bulk transport of `liqueed gas at low temperature, the combination of a hull, a mainv deck, a plurality Vof transverse liquid-tight bulk heads dividing up the cargo space below themain deck intoa plurality of Vseparatemain hold compartments, Va.

rlurain/Y Voffheavily-@USB1ated main tanks fer liqlieersi 4 gas cargo, vsaid tanks being disposed in a closely-spaced row onejin each of the hold compartments, a plurality of deck tanks disposed on the main deck, a ring main, connections `from each of the deck tanks to the ring main, connections from the ring main to the space around the cargo tank in each of the hold compartments and valve means in said connections operable to enable liquid in the deck tanks to be discharged into anyone selected hold compartment.' t

2. In a marine tanker for the bulk transport of liquid methane at low temperature, the combination of a hull, a main deck, a plurality of liquid-tight bulkheads divid- V ing up the cargo space below the main deck into a plurality of separate main hold compartments, a plurality of heavily-insulated tanks for liquid methane cargo, said tanks being disposed one in each of the hold compartments, a plurality of storage tanks for holdfooding liquid disposedat a level substantially above the level of the cargo tanks, hold-flooding connections from all the storage tanks to all the spaces around the cargo tanks in the hold compartments and valve means in said connections operable to enable the liquid in the storage tanks to be discharged Aunder gravity into any of the hold compartments.

3. In a marine tanker for the bulk transport of liquid methane at low temperature, the combination of a hull, a main deck, a plurality of transverse liquid-tight bulkheads dividing up the cargo space below the main deck into a plurality of separate hold compartments, a plurality of heavily-insulated tanks for liquid methane cargo said tanks being disposed one in each of the hold compartments, a plurality of deck tanks for hold-flooding liquid disposed on the main deck, a hold-ooding liquid line, connections from each of the deck tanks to said liquid line, connections from said liquid line to the space around the cargo tank'in each of the hold compartments and valve means in said connections operable to enable liquid in all the deck tanks to be discharged under gravity into any one selected hold compartment.

4. A tanker as claimed in claim 3, wherein the deck tanks are connected to a ships ballast system and oil lcargo system so that the deck tanks can be charged when required. Y Y

5. A .tanker as claimed in claim 3, said heavily-insulated tanks comprising a plurality of main cargok tanks arranged in a closely-spaced row along the fore-and-aft center line of the vessel each tank extending at its Widest part across substantially the full Width of the vessel, and wherein at least someof Vthe tankshave portions of reduced crosssection projectingV up through the main deck and enclosed'within a turret structure narrower than and above said deck, and at least some of the deck tanks are disposed inthe turret between said portions of the cargo tanks.

6. A tanker as claimed in claim 5, wherein smaller wing cargo tanks are located Wholly below the main deck and onopposite sides of the hull in spaces between-the all installed in individual hold compartments having ilooding connections from the deck tanks.

7. In a marine tanker for the bulk transport of'liqueed 'natural gas at low temperature, the combination of a hull, a main deck, a plurality of transverse bulkheads dividing up the cargo space below the main deck into a plurality of separate main hold compartments, a plurality of heavily-insulatedA main tanks for liquefied gas cargo said tanks being disposed in a closely-spaced row one in each of the hold compartments with upright axes intersecting the fore and aft center line of the vessel, a plurality of smaller heavily-insulated Wing tanks for liq- "ueed' gas cargo, said wing tanks being disposed in wing hold-flooding line, connections from said liquid storage to the hold-flooding line, connections from the hold-flooding line to the space around the cargo tank in each of the hold compartments and valve means in said connections operable to enable liquid in said liquid storage to be discharged into the hold compartment.

8. ln a marine tanker for the bulk Itransport of liquid methane at low temperature, the combination of a hull, a main deck, a plurality of transverse bulkheads dividing up the cargo space below the main deck into a plurality of separate hold compartments, a turret decknarrower than the main deck and extending fore-and-aft above the main deck over said hold compartments, a plurality of heavily-insulated tanks for liquid methane cargo each having a coniiguration that is mainly of upright cylindrical form, said tanks being disposed in a row one in each of the hold compartments with their upright axes intersecting the fore-and-aft center line of the vessel and each tank being stepped in at at least one level near the top thereof so as to give the tank a centrally-placed narrow neck portion with the full-diameter portion of the tank disposed wholly below the main deck and the neck portion projecting above the main deck and lying within the contines of the portion of the deck width delined by the turret deck, at least some of said tanks having between the neck and the full-diameter portion a stepped section of an intermediate diameter which intermediate diameter stepped section commences just below the main deck but is otherwise located between the turret deck and the main deck and is of a diameter as large as the width of the turret deck will allow, a plurality of deck tanks disposed on the main deck underneath the turret deck and between the intermediate diameter sections of the cargo tanks, hold-ilooding liquid line connections from all the deck tanks to all the spaces around the cargo tanks in the hold compartments and valve means in said connections operable to enable liquid in all the deck tanks to be discharged into any one selected hold compartment.

9. `In a marine tanker for the bulk transport of liquid methane at low temperature, the combination of a hull, a main deck, -a plurality of transverse liquid-tight bulkheads dividing up the cango space below the main deck into a plurality of separate main hold compartments, a turret deck narrower than the main Ideck and extending fore-and-aft above the main deck in uninterrupted manner over all said hold compartments, turret side structure enclosing the space between the main and turret decks, a plurality of heavily-insulated main tanks for liquid methane cargo each having a configuration that is mainly of upright cylindrical 4form and occupies at its widest part substantially the whole available width of the vessel,

said tanks being Adisposed in a closely-spaced row one in each of the hold compartments with their upright axes intersecting the fore-and-aft centre line of the vessel and each tank being stepped in at at least one level near the -top thereof so as to give the tank a centrally-placed narrow neck portion with the full-diameter portion of the tank disposed Wholly Ibelow the main deck and the neck portion projecting above the main deck and lying Within the contines of the portion of the deck width defined by the turret structure, at least some of said tanks having between the neck and the full-diameter portion a stepped section of an intermediate diameter which intermediate diameter stepped section commences just below the main vdeck but is otherwise wholly located within the turret structure and of a diameter as large as the enclosed space within the turret structure will allow, those tanks Iwith such an intermediate diameter section having their nar- 'row neck portions projecting up above the level of the turret deck, a plurality of smaller heavily-insulated wing tanks for liquid methane cargo each having a substantially upright cylindrical coniiguration, said wing tanks being disposed wholly below the main deck in the 'wing spaces between the main tankstolwards the sides of the ship and said transverse bulkheads being formed around said wing tanks to enclose each wing tank in its own separate wing hold compartment, a plurality of deck tanks disposed on the main deck Within the turret structure and between the intermediate diameter sections of the main cargo tanks, a ring main, connections from each of the deck tanks to the ring main, connections from the ring main to the space around the cargo tank in each of the lhold compartments and valve means in said connections operable to enable liquid in tanks to be discharged into any 4one selected hold cornpartment.

References Cited in the le of this patent UNITED STATES PATENTS 666,076 Wailes et al. Ian. l5, 1901 689,782 Blanchard Dec. 24, 1901 1,085,086 Jack Ian. 20, 1914 2,798,364 Morrison July 9, 1957 2,896,416 Henry July 28, 1959 2,933,902 Howard Apr. 26, 1960 FOREIGN PATENTS 1,060,735 France Nov. 18, 1953 all the deck 

